[CORE] Support cacheable & non-cacheable access in vmm_host_memory_xxx() API

Currently, vmm_host_memory_xxx() and vmm_guest_memory_xxx() APIs only
supported cacheable access but in-real life we might also require
non-cacheable access from this APIs. For example, file contents loaded
by "vfs host_load" and "vfs guest_load" commands should be updated
in RAM directly and should not reside in caches.

This patch extends vmm_host_memory_xxx() and vmm_guest_memory_xxx() APIs
to support both cacheable and non-cacheable access.

Signed-off-by: Anup Patel <anup@brainfault.org>